Replacement of sub sea blow out preventer packing units

ABSTRACT

Apparatus and method to enable well blow-out preventer packer replacement at a sub-sea well head location.

[ 1 June 26, 1973 United States Patent Murmun et al.

[51] Int. E2lb 33/035 [58] Field of 166/.5, .6; 25l/l;

[ REPLACEMENT OF SUB-SEA BLOW-OUT PREVENTER PACKING UNITS [75]Inventors: Fernando Murman, Palos Verdes [5 6] References Cited UNITEDSTATES PATENTS Peninsula; George E. Lewis, Arcadia; Allen I. Dunn, LosAngeles; Charles E. OBrien, Whittier, all of Calif.

3,589,667 6/1971 3,543,847 12/1970 l'laeber 3,561,723

[73] Assignee: Hydril Company, Los Angeles,

Calif.

Primary Examiner-James A. Leppink Attorney-White, l-laefliger 8L Bachand[22] Filed: June 14, 1971 2] Appl. No.: 153,093

[57] ABSTRACT Apparatus and method to enable well blow-out pre- RelatedU.S. Application Data [62] Division of Ser. No. 60,066, July 31, 1970,Pat. No.

venter packer replacement at a sub-sea well head location.

19 Claims, 15 Drawing Figures PATENTED JUN 2 6 I975 SHEEI 1 [1F 7 ll/Umn J! PATENTEDJUNZS ms 3.741.295

sum-a or 7 PAIENIEDauuzs um SHEEN; 0F 7 g E LCwU M "0 w f II. Z :l.

W i a W Pmmninmzs ms 3 SHEET 5 U? 7 REPLACEMENT OF SUB-SEA BLOW-OUTPREVENTER PACKING UNITS This application is a division of Ser. No.60,066 filed July 31, 1970, now US. Pat. No. 3,662,823.

BACKGROUND OF THE INVENTION This invention relates generally toreplacing blow-out preventer packers in housings therefor, and moreparticularly concerns such replacement carried out at subsea well headlocations.

The replacement of blow-out preventer packers located at off-shoresub-sea installations is presently extremely expensive due to therelatively great amount of time involved in carrying out suchreplacement. For example, up to twenty hours and more time is consumedin pulling to the surface the entire stack of equipment at the wellhead, replacing the preventer packer, and lowering and re-installing thestack at the ocean floor. Accordingly, there is a great need for methodand apparatus for carrying out a packer replacement operation withoutrequiring such elevation and loweringof the entire stack. 1

SUMMARY OF THE INVENTION It is a major object of the invention toprovide a solution to the above problem, enabling blow-out preventerpacker replacement at the sub-sea well head location and at greatlyreduced expense. Basically, and in its method aspects, the inventioncontemplates the retrieval of the packer from an annular body to whichpacker hold-down means is releasably attached. The method includes thesteps of elevating the hold-down means relative to the body to exposethe packer for removal; advancing a packer retrieval tool laterally anddownwardly to penetrate the body, and effecting lifting attachment ofthe tool to the packer; and retracting the tool, with packer attached,upwardly and laterally to lift the packer out of vertical alignment withthe body, enabling its subsequent elevation to the surface. As will beseen, the lifting tool may become magnetically attached, or mechanicallyattached to the packer to lift it from the body or housing at sub-sealocations, and the hold-down means may be preliminarily elevated as bylifting a tubular riser to which the hold-down means is attached.Additional steps may include the lowering of a replacement packer to alocation proximate the preventer body from which the original packer hasbeen retrieved; advancing the tool, with replacement packer attached,laterally and downwardly to penetrate the body; detaching the tool fromthe packer; retracting the tool upwardly and laterally from the body;and lowering the hold-down means for attachment to the body.

In one important apparatus aspect, the invention comprises an annularbody and a fluid pressure responsive packer actuator movable verticallyin the body; an annular packer received downwardly in the body andsupported by the actuator for radial construction and expansion;hold-down means carried to block upward displacement of the packer inresponse to upward movement of the actuator; and other means foreffecting locking of the hold-down means to the body and unlockingthereof to permit upward removal of the holddown means from the body,followed by upward withdrawal of the packer. Typically, the hold-downmeans may have telescopic interfit with the body, and referred to othermeans may include latch structure carried by the hold-down means formovement into and out of locking position relative to the body. Also, afluid pressure responsive member may be carried by the holddown meansfor movement in one direction to urge the latch structure into lockingposition, and for opposite direction movement to allow lateral movementof the latch structure out of said locking position. In this regard, thebodyis typically mounted in a sub-sea well head stack and a tubularriser is connected to the hold down means for elevating same to aposition in which the packer becomes upwardly exposed for removal fromthe body. The riser connection may advantageously comprise a ball andsocket joint allowing for some misalignment and preventing excessivemoment exertion on the body and stack.

Another important apparatus aspect of the invention concerns theprovision of packer retrieval means located generally laterally of thebody and riser and having a part bodily movable laterally and downwardlyinto the body for lifting the packer from the body. Such retrieval meansmay include a carrier that is vertically movable relative to the stack,as for example to and from the surface, and an arm operatively connectedto the carrier and supporting the part for bodily movement betweenlowered position in which the retrieval part projects within the annularbody for operative connection to the packer, and raised position inwhich the part and packer are laterally offset from the stack forelevation by the carrier to the sea surface. As will be seen, the armmay have pivotal connection to the carrier, and locating means may beprovided for locating the carrier in predetermined offset relation tothe stack in response to lowering of the carrier laterally of the stack.

Further, retention means may be provided on the carrier to interfit thepacker in raised position thereof and in response to carrier elevation,thereby to positively retain the packer on the carrier during elevationto the surface. Such functioning is facilitated with unusual advantageby means of a retention plug sized to upwardly penetrate the packercentral passage, and by pivotally suspending the packer lifting partfrom the arm, as will be seen. In addition, the carrier may comprise afirst section connected to the retention means, and a second section towhich the arm has pivotal connection, the second section being movablevertically relative to the first section to effect the interfit of theretention means with the packer in response to initial elevation of thecarrier relative to a portion of the 10- cating means attached to thestack.

These and other objects and advantages of the invention, as well as thedetails of illustrative embodiments, will be more fully understood fromthe following description and drawings, in which:

DRAWING DESCRIPTION FIG. 1 is a vertical side elevation showing asub-sea well head assembly;

FIG. 2 is an elevation showing a retrieved packer in its carrier;

FIG. 2a is a view similar to FIG. 2, showng the retrieved packerretained on the carrier;

FIG. 3 is an enlarged section taken on line 3--3 of FIG. 1;

FIG. 4 is an enlarged elevation taken in section on lines 4-4 of FIG. 1;

FIG. 5 is an enlarged plan view taken on lines 5-5 of FIG. 1;

FIG. 6 is an enlarged fragmentary section taken on lines 6--6 of FIG. 1;

FIG. 7 is a vertical elevation taken in section showing a completeblow-out preventer assembly constructed in accordance with theinvention;

FIG. 8 is an enlarged fragmentary showing of the hold-down meansillustrated in FIG. 7;

FIG. 9 is a vertical elevation taken in section showing another modifiedhold-down means;

FIG. 10 is an enlarged fragmentary showing of the hold-down means ofFIG. 9;

FIG. 11 is an enlarged front elevation of the FIG. 1 carrier forretrieving and installing a blow-out preventer packing unit;

FIG. 12 is a vertical elevation taken on line 12-12 of FIG. 11; and

FIGS. 13 and 14 are vertical elevations taken in section to show othermethods of retrieving (or installation) attachment to a packer.

DETAILED DESCRIPTION Referring first to FIG. 1, the new type blow-outpreventer assembly 90 is shown connected in a sub-sea stack 100. A risersystem 102 extends above the stack andis connectible thereto by aconnector 103 which also serves as a packer hold-down means as will bedescribed. Riser pipe 87 extends into the sea surface, and typically toa drilling barge 104 or other installation, for conducting productionfluid to the surface, as within production tubing installable withinpipe 87 by known techniques, and better indicated at 86 in FIG. 7.

Turning to FIG. 7, the control head or preventer assembly, generallyindicated at 10, includes a body member 11, having concentric bores 12,13 and 14, which are of progressively increased diameters. Releasablehold-down means 16 is releasably held to the body member intelescopically interfitting relation and in such a position that theface 19 of flange 20 engages the upper end 21 of the body member 15, thelatter and hold-down annulus 18 being packed off at 22. Annulus 18 has abore 23 which may be of the same diameter as, and concentric with, bodybore 12. Sunk in the upper face of annulus 18 are bolt holes 24 for theattachment of a flange 105 to which the riser 87 is fastened as bywelding at 106, the bolts being shown at 107. An annular groove 25, inthe upper face of a sleeve 108 is adapted to receive a sealing ring 25afor sealing engagement with the riser. Sleeve 108 interfits the annulus18 to define a hollow 109, reducing the weight of the hold-down means16.

The lower neck 26 of body member 1 1 has an attach ment flange 27whereby connection is made through bolts 28 to the flange 29 or anyother suitable fitting.

The body 11 has an annular, upstanding flange 38 which engages thepacker actuating member 39 at 40 to limit the extent of downwardmovement of said member. The actuator 39 has a piston portion 41, havingpiston-fit in bore 14, and the actuator is extended opening,respectively, from those chambers. External pipes 51 and 52 open toports 49 and 50, respectively. Note that the outer diameters 14 ofchambers 47 and 48 are equal, and the inner diameters 13 and 37 of thesechambers may be equal, for balancing purposes. Means to controllablydeliver fluid pressure to chambers 47 and 48 is indicated generally at110.

The actuator 39 has a downwardly and inwardly tapering conical bore 53,and the actuator portion 43 which defines this bore may be consideredbroadly as an internal, conical wedge, or as a packer-constrictingelement.

Packer P includes a massive annulus or sleeve 55 of an elastomer and,preferably, resilient material such as rubber or Neoprene. In mostinstances, it is intended that a single packer be adapted for repeatedopening and closing operations, and therefore it is preferable that ithave relatively high resilient characteristics, so it may beself-restoring to open position when the constricting force is removed.From this point on in the description, it will be assumed that thepacker has such resilient characteristics, but this assumption is notconsidered as limitative on my broader claims. It has been found thatrubber having a durometer hardness of about 75 is suitable for generaluse in my packer but, again, this specification of relative hardness isnot to be considered as limitative. The packer is shown as an unsplit,continuous annulus, but it will be understood that the disclosure is notlimited to a packer wherein there is no split, so long as there is noangularly extending gap interrupting the continuity of the packer attimes when it is inwardly contracted into sealing engagement withmembers positioned within its bore.

Included in the make-up of the packer is a series of rigid,rubber-flow-control elements 56. These elements may take differentforms, and they are individually movable bodily with the rubber in itsmovement of contraction and expansion and also, to a limited extent,movable individually with respect to the rubber as will later appear.Taken together, the rigid control elements may be considered as aradially expansible and contractible armature embedded and bonded withinannulus 55.

Molded annulus 55 has an outer conical face 57 which is complementary toactuator bore 53, and a bore which has a central, substantiallycylindrical portion 59 and oppositely inclining upper and lower portions60 and 61, respectively; the outward flare, in each case being towardthe associated end of the annulus.

It will be seen that each element 56 comprises top and bottom plates 63and 64, respectively, rigidly connected by vertical rib 65, the outerfaces 66 of the plates and the outer face 67 of the rib havingsubstantially the same degree of taper as bore 53 and annulus face 57.Or plates 63, 64 may be considered as transverse flanges on rib 65.Elements 56, which may be of steel, bronze, or any other suitable rigidmaterial, are preferably positioned in the rubber at the time of molding and, preferably, the rubber and the elements are bonded together bythe use of suitable adhesive during the molding process. The plates ofthe control elements are sectorial in shape, as viewed in plan, and arearranged in a circular series, with spaces left between the opposingside edges of the plates, both top and bottom. The plates are so sizedthat the two opposed side edges of adjacent elements are spaced apart,if following that as the elements move radially inward, the spacesbetween these, will diminish to form a line contact from end to end ofthe plates. This will prevent the rubber which will flow during theconstriction of the annulus from being pinched off at the radiallyinward ends of the plates.

The annulus 55 is molded so its outer annular portion 72 projectsradially outward beyond the outer faces 66 of the plates, it followingthat these metallic faces do not engage the wall of actuator bore 53.For purposes of later description, annular portion 72 is considered asbeing that portion which extends radially from face 57 to the outerfaces 67 of ribs 65.

The packer is lowered, while hold-down means 16 is I elevated, into theposition of FIGS. 1 and 7, the annulus 55 nicely fitting the upperportion of bore 53 without requiring appreciable radial constriction ofthe annulus. For positively limiting the downward movement of theannulus, a stop is provided in the'form of tube 74 which is retained inhousing bore 12a. The upper end of the tube provides the packer stop.The bore 75 of this tube is of the same diameter as bores 12 and 23, andthe tube is annularly spaced from both piston portion 42 and the lowerend of actuator wedge-portion 43. Ports 76 open from bore 75 to chamber77, which latter is annularly defined by the tube and the actuatorportion 42 while it is retained endwise by bolts 78.

When means 16 is subsequently secured in place, its horizontalunder-surface 79 provides a stop for limiting upward movement of thepacker, the upper plates 63 of control elements 56 sliding over thissurface. as the packer is radially constricted or expanded.The-undersurface 79 and the upper end of tube 74 thus form verticallyspaced stops which prevent appreciable vertical movement of the packerwith relation to the body member 1 1.

it will be seen that the radial constriction of the packer isaccomplished by virtue of relative vertical movement between the packerand the actuator. While the illustrated embodiments show this relativemove ment as brought about by holding the packer against verticalmovement with respect to the body member and then moving the actuatorvertically with respect to the housing and packer, it will be understoodthe arrangement and operation may be reversed, and indeed may varydepending upon the type of blow-out preventer to be used.

An important aspect of the invention concerns the construction of thehold-down means 16 to permit its upward removal as by the riser 87, andat the sub-sea stack location, thereby to permit retrieval of a thusexposed packer and installation of a new packer in the body 1 1. In thisregard, other means on the hold-down means 16 is operable to effectlocking of the hold-down means to the body and unlocking thereof, suchother means typically including latch structure carried by the hold-downannulus 18 for movement into and out of locking position relative to thebody, as for example member 11 and 15.

In the FIG. 7 and 8 example of such latch structure, a series of latchdogs 1 12 may be circularly supported on the shoulder 113 of thehold-down annular insert 18, for radial movement bringing the latch dogteeth 114 into meshing engagement with the annular teeth 115 formed inthe bore 116 of member 15. Vertical pins 117 fit in slots 118 in thedogs to accommodate such movement of the dogs, while retaining them tothe insert annulus 18, the pins being carried by cylinder member 119.

The referred to other means for effecting locking of the hold-down meansto the body may also include a fluid pressure responsive member carriedby the holddown means for movement in one direction (as for exampledownwardly) to urge the latch dogs into the described meshing or lockingcondition, and for movement in the opposite direction to allow lateralmovement of the dogs out of locking position. In the FIG. 7 and 8example, the fluid pressure responsive member is shown to comprise theannular actuator 120, the lower terminal of which includes a cam surface121 to engage cam surfaces 122 of the dogs upon downstroking of theactuator, thereby to effect interlocking of the teeth 114 and 115. Lowerterminal 123 also includes a slight downward and inward taper 124 toengage the dogs upon continued down-stroking, thereby to effect finalforcible tightening of the interlock of the teeth, and to frictionallylock the actuator to the dogs during normal sub-sea operation of theblow-out preventer. 1

Actuator includes a piston 126 working in the cylinder, with seals 127sealing off there between. Also, the actuator has a slide fit on thesurface 128 of the annular insert 18, and seals 129 and 130 seal offbetween the actuator and the cap 20, and the actuator and the cylinder,as shown. Accordingly, pressure chambers are formed at 132 and 133, atopposite vertical sides of the piston 126, to receive pressure from oneof the pressure bottles 134 in FIG. 1, or from the surface, and viaappropriate piping 135 and 136, and four-way valving '137 controllablefrom the surface as via electrical line 300 and actuator 137a. Pressureadmitted to chamber 132 urges the actuator 120 downwardly to effect theinterlock, as described; at which time fluid from chamber 133 may beexhausted to the sea; and pressure admitted to chamber 133 urges theactuator upwardly to release the interlock, at which time fluid fromchamber 132 may be exhausted to the sea. The latter movement of theactuator allows the dogs 112 to be cammed inwardly by engagement withthe member 15 at 131 as the hold-down means is lifted out of the body 11as by the riser, when replacement of the packer is to be effected.

FIGS. 9 and 10 show a connection of the riser 87a to the hold-down means16a in the form of a ball 140 attached to the riser, and socket 141 and141a formed by the annulus 142 and cap 143, the latter two elementsbeing integrally connected as by bolts 144. The ball contains a throughpassage 145 in registration with the bore 146 of the riser and theopening 147 defined by the packer P. Pivoting of the ball in the socketallows for limited vertical misalignment as between the riser and thehousing or body 11 of the preventer, whereby transmission of bendingmoments to or from the stack 100 are relieved, and the boltedinterconnections of the elements of the stack and in the riser are notoverstressed. Engagement of a lug 148 on the ball with the sides of aslot 149 is to limit relative rotation of the riser and the hold-downmeans.

Also, the structure operable to displace the latch dogs 112a is somewhatmodified. As illustrated, the actuator 120a now works up and down withinthe bore 151 defined by the cylinder 152, the upper flange 153 of whichseats on the shoulder 154 of the body member 11a. A compressibleelastomer annulus 154a seals off between the actuator and the bore 1 16of member 11a,

whereby sea water cannot continue to gain access to the latch dogs fromthe exterior once the hold-down means is assembled in place. Upperpressure chamber 155 is formed between the actuator piston 156 and thering 157, and lower pressure chamber 158 is formed between the actuatorpiston 159 and that ring, there being suitable seals as at 160 164.Down-stroking pressure is provided via porting 165 and 166, whereasup-stroking pressure is supplied via porting 167 and 168. A bleed port169 communicates between the chamber 170 at the lower end of the piston159 and the chamber 170a at the upper end of piston 156 to preventdifferential pressure build-up in these chambers as the piston moves.The lack of a gasket at surface 128 in FIG. 8 allows pressure balancebetween chambers 400 and 401. (Elements 114a, 115a and 124a in FIG.correspond to 114, 115 and 124 in FIG. 8).

Turning now to FIGS. 1 6, 11 and 12, a further aspect of the inventionconcerns the provision of packer retrieval means located generallylaterally of the blowout preventer assembly 10, and riser 87, and havinga part bodily movable generally laterally and downwardly into the body 11 for lifting the packer therefrom after preliminary elevation of thehold-down means by the riser. Such elevation may be accomplished fromthe derrick on the barge or vessel 104, after the hold-down means ispressurized to relieve the latch dogs for inward movement, as described.

The referred to lifting part is exemplified in FIG. 1 by anelectromagnet 160 pivotally suspended at 161 from a lifting arm 162operatively connected to a carrier 163, the latter being verticallymovable relative to the stack. As illustrated, the electromagnet 160 issupported for bodily movement between lowered position (FIG. 1) in whichit projects downwardly within the annular body 11 for operativeconnection to the packer, and raised position in which the electromagnet(or other part) and the packer are laterally offset from the stack forelevation by the carrier to the sea surface, FIG. 2a showing the stowedposition of the packer during vertical travel with the carrier, eitherup or down. Electromagnet 160 typically may include a coil 165 extendingbetween annular north and south pole elements 166 and 167, the lowerterminals of which are magnetically attachable to the top plates 63 ofthe packer, where such plates consist of steel or other magnetizablematerial. An electrical control cable from the surface is indicated at168. Note that the positioning of the carrier 163 and arm 162 are suchthat the electromagnet 160 is approximately centered over the packer inlowered position, at which time the coil 165 may be electricallyenergized. During vertical travel of the packer in the carrier, theelectromagnet need not be electrically energized due to the stowedcondition of the packer, as will be explained.

The carrier in FIGS. 1, 2, 2a, 4 6, 11 and 12 comprises a first framesection 169 including laterally spaced vertical members 170 and 171, andcross members 172, 173 and 174; the, carrier also includes a secondframe section 175 which is Ushaped and has vertical and horizontalmembers 176, 177 and 178. The arm 162 has laterally spaced members 162aand l62b pivotally connected at 179 and 180 to the second frame members176 and 177, as better seen in FIG. 5. An actuator 181 on the carrier isconnected at 184 to the arm and is operable to displace the arm betweenlowered position as seen in FIG. 1 and raised position as seen in FIG.2.

The carrier carries what may be referred to as retention' means operableto interfit the packer in its raised position and in response toelevation of the carrier, for retaining (i.e. stowing) the packer duringits elevation to the surface, and likewise to stow a replacement packerbeing lowered from the surface to the sub-sea stack site. In thisregard, FIG. 2 a shows one unusually advantageous retention means onwhich the packer is stowed during vertical travel of the carrier. Asthere shown, the retention means comprises a plug 276 mounted on carriercross members 173 and sized for upwardly penetrating the central passageformed by the packer lower plates 64, with loose interfit of suchplates. Such penetration is effected in response to initial raising ofthe carrier section 169 as by lifting cable 278 attached to the carriervia coupling structure 279 son of FIGS. 2 and 2a. Note in FIG. 4 thetypical tongues 182 on members 176 and 177 received in the verticalslots or grooves 183 in members and 171; the pivotal mounting 184a ofthe actuator 181 to the cross member 178, and the pivotal connection at184 of the actuator to yoke 185 connected to the arm sections'l62a and162b. 7

.Upon lowering of the carrier 163 to position seen in FIG. 2, the secondframe section 175 is elevated relative to the first frame section 169 inresponse to centered engagement of a lifting element with a locatingelement, assuming the operating position shown in FIG. 2. In thisregard, the lifting element may comprise a rod connected to the secondframe section 175 as shown and projecting downwardly through a guidetube 191 to protrude at 190a for centered engagement with the downwardlytapering centering receptacle 192 mounted on the stack arm 193. That armis fixed relative to the stack 100 and base 194, as shown. The firstframe section 169 continues to lower, following such engagement, untilthe tube 191 bottoms on the receptacle, as shown. Accordingly, thesecond section 175 is lifted by a predetermined amount relative to thefirst section 163, thereby to free a replacement packer from theretention means 276 during the replacement operation, and also thecarrier is precisely located in lateral relation to the housing 11,enabling desired extension and lowering of arm 162 to enter the part160, and a replacement packer, into the open-topped housing,as shown onFIG. 1.

Azimuthal centering of the carrier relative to the housing is assured bythe guiding of the carrier on the vertical guide cables 200 and 201 asseen in FIG. 3. For this purpose, the cross-arm 202 integral with thecarrier 163 has cable passing sleeves 203 and 204, as shown, a verticalrod 205 connecting the arm 202 with the carrier first frame section 169.Coupling 279 slides vertically on rod 205, and lifts upwardly againstcross-arm 202, upon raising of the carrier. The connection 161 of thearm to the packer lifting part 160 may be effected by trunnions 161a and161b, respectively, on the arm sections 162a and 162b, as seen in FIG.5. Other guide cables attached to base 194 are shown at 200a and 201a.

FIGS. 11 and 12 show the provision of an actuator fluid pressurereservoir 209 and valve 210 mounted on the carrier 163, with a line 211connecting the reservoir and valve, and lines 212 and 213 connecting thevalve with opposite ends of the actuator cylinder 214. The valve motor215 is controlled from the surface, as by control means 216. Notesurface control means 217 which is connected with cables 168 and 216,and also to control cables 300 and 301 to controls 137a and 110 as shownon FIG. 7 and 8.

FIGS. 13 and 14 illustrate alternate forms of parts operable to lift andlower packers while suspended from the arm 162. In FIG. 13, the part 219comprises a plug 220 downwardly insertible into a central opening orbore 59 formed by the packer elastomer body 55. One or more liftingelements 221 are carried by the plug body 222 to be extensible therefromin under-fitting relation to the inner terminals of the upper plates 63,as shown, for mechanically coupling the plug to the packer. Suchelements 221 may comprise plungers working in upwardly and outwardlyangled bores 223, with pistons 224 integral with the plungers andworking in cylinders 225. Fluid pressure delivery to the latter from areservoir 226 is controlled by a valve 227, with valve motor 228operated from surface control at 217 in FIG. 1. Elements 226 228 may bemounted on the carrier, in a manner similar to elements shown in FIGS.11 and 12. Ducts and porting between the valve and cylinders 225 areshown at 230 232. A closure plate 233 attached to the plug 220 seals theporting 232 and cylinders 225, and the plug 220 carries an upper flange234 which overlaps and interfits the upper plates 63 of the packer unit.

Similarly, fluid may be delivered from valve 227 via line 235 to thechamber 236 communicating with the opposite sides of the pistons 224,for retracting the filters.

The packer lifting part 240 in FIG. 14 likewise comprises a plug 241fitting downwardly into central opening or bore 59 formed by packer body55', an upper flange 242 integral with the plug fitting over the packerunit plates 63. The lifting elements 243 in this case are horizontallyslidable within glands 244 sealing off between lifter retractionchambers 245 and the plug exterior. Pistons 246 carried by the lifterswork in'cylinders 247 to which fluid pressure may be supplied via line248 for extending the lifters into the positions shown. Fluid forretracting the lifters is supplied via line 249 to chambers 245, withwhich the opposite sides of the pistons communicate via ports 245a.

In operation, the basic method of the invention includes the steps ofelevating the packer hold-down means relative to the packer housing orbody tovertically expose the packer for removal; moving a packerretrieval element laterally and downwardly to penetrate the body andeffecting lifting attachment of the element to the packer; and movingthe element with packer attached thereto upwardly and laterally to liftthe packer out of vertical alignment with the body, for subsequentelevation of the packer to the surface, all of these steps being carriedout underwater. As described, the attachment of the lifting element orpart to the packer may be magnetically or mechanically effected.Further, a replacement packer may be lowered to predetermined locationproximate the preventer body, the packer may then be lowered into theopen-topped body followed by detachment of the lowering or lifting partfrom the packer and return of the tool out of alignment with the body,and the hold-down means may be replaced. Preliminarily, the well may beclosed off at a level below the packer to block communication with thesea. Conventional blind rams 410 are operable to effect such closure, asvia control cables 411.

In FIG. 1, the item 400 is a television camera in a circuit having asurface viewing screen to enable viewing of the packet replacementoperation.

We claim:

1. In well blow-out preventer apparatus, the combination comprising a.an annular body adapted to pass well equipment,

b. a fluid pressure responsive packer actuator movable in the body,

c. an annular packer received downwardly in the body and supported forgenerally radial constructionand expansion in response to said actuatormovement,

d. hold-down means carried to block upward displacement of the packer inresponse to movement of the actuator,

e. other means for effecting locking of the hold-down means to the bodyand unlocking thereof to permit upward removal of the hold-down meansfrom the body followed by withdrawal of the packer therefrom, i

f. said hold-down means having telescopic interfit with said body, andsaid other means including latch structure carried by the hold-downmeans for movement into and out of locking position relative to saidbody, and

g. said other means including a fluid pressure responsive member carriedby said hold-down means for movement in one direction to urge said latchstructure into said locking position, and for movement in the oppositedirection to allow lateral movement of the latch structure out of saidlocking position.

.2. The combination of claim 1 wherein said'latch structure includes acircular series of latch dogs received downwardly within said body on anannular insert portion of said hold-down means.

3. The combination of claim 2 wherein the lower terminal of said annularinsert portion of said hold-down means provides a stop against which theupper surface of the packer is engageable, said packer including anelastomeric body and metallic inserts carried thereby and having upperplates defining said upper surface.

4. The combination of claim 1 including a sub-sea well head stackmounting said body, and a tubular riser extending upwardly from saidhold-down means.

5. The combination of claim 4 wherein said riser has connection to saidhold-down means for elevating said hold-down means relative to said bodyand to a position in which said packer is upwardly openly exposed forremoval from the body. I

6. In well blow-out preventer apparatus, the combination comprising a.an annular body adapted to pass well equipment,

b. a fluid pressure responsive packer actuator movable in the body,

c. an annular packer received downwardly in the body and supported forgenerally radial constriction and expansion in response to actuatormovement, I

e. other means for effecting locking of the hold-downmeans to the bodyand unlocking thereof to permit upward removal of the hold-down meansfrom the body followed by withdrawal of the packer therefrom, and I f. asub-sea well head stack mounting said body, and

a tubular riser extending upwardly from said holddown means, said riserhaving connection to said hold-down means for elevating said hold-downmeans relative to said body and to a position in which said packer isupwardly openly exposed for removal from the body, and said riserconnection to the hold-down means comprising a ball and socket, the balldefining a vertical passage above an opening defined by the packer.

7. The combination of claim 6 wherein said holddown means has telescopicinterfit with said body, and said other means includes latch structurecarried by the hold-down means for movement into and out of lockingposition relative to said body.

8. The combination of claim 7 wherein said other means includes a fluidpressure responsive member carried by said hold-down means for movementin one direction to urge said latch structure into said lockingposition, and for movement in the opposite direction to allow lateralmovement of the latch structure out of said locking position.

9. The combination of claim 6 including packer retrieval means locatedgenerally laterally of said body and riser and having a part bodilymovable laterally and downwardly into said body for lifting the packertherefrom after preliminary elevation of the hold-down means by saidriser.

10. The combination of claim 9 wherein said part comprises anelectromagnet.

11. The combination of claim 9 wherein said part comprises a plugdownwardly insertible into a central opening defined by the packer, andincluding a lifting element carried by the plug for movement into packerlifting position.

12. The combination of claim 9 including vertically extending guy wiresto which the packer retrieval means has guided connection for elevationand lowering thereof relative to the stack.

13. The combination of claim 9 wherein said packer retrieval meansincludes a carrier that is vertically movable relative to the stack, andan arm operatively connected to the carrier and supporting said part forsaid bodily movement between lowered position in which said partprojects within said annular body for operative connection to thepacker, and raised position in which said part and the packer arelaterally offset from the stack for elevation by the carrier to the seasurface.

14. The combination of claim 13 wherein said arm has pivotal connectionto the carrier, and including 10- cating means for locating the carrierin predetermined relation to the stack in response to lowering of thecarrier laterally of the stack.

15. The-combination of claim 14 including retention means on the carrierto interfit the packer in raised position thereof and in response toelevation of the carrier, for positive retention of the packer on thecarrier during elevation to the surface.

16. The combination of claim 15 wherein said retention means comprises aplug sized to upwardly penetrat e the central passage formed by thepacker in said raised position.

17. The combination of claim 15 wherein said'carrier comprises a firstsection connected to said retention means, and a second section to whichthe arm has said pivotal connection, the second section being movablevertically relative to said first section to effect said interfit of theretention means with the packer in response to initial elevation of thecarrier relative to a portion of said locating means attached to thestack.

18. The combination of claim 13 wherein said part is pivotally suspendedfrom said arm.

19. The combination of claim 13 including an actuator on the carrier andoperable to displace said arm between positionscorresponding to saidraised and lowered positions of said part.

m n w UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,741,295 Dated June 26 1973 Inventor(s) Fernando Murman, GeorgeE.Lewis, Allen I. Dunn and Charles E. O'Brien It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 10, line 17; "body and supported for generally radial construcashould read body and supported for generally radial constric- (SEAL)Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. In well blow-out preventer apparatus, the combination comprising a.an annular body adapted to pass well equipment, b. a fluid pressureresponsive packer actuator movable in the body, c. an annular packerreceived downwardly in the body and supported for generally radialconstruction and expansion in response to said actuator movement, d.hold-down means carried to block upward displacement of the packer inresponse to movement of the actuator, e. other means for effectinglocking of the hold-down means to the body and unlocking thereof topermit upward removal of the hold-down means from the body followed bywithdrawal of the packer therefrom, f. said hold-down means havingtelescopic interfit with said body, and said other means including latchstructure carried by the hold-down means for movement into and out oflocking position relative to said body, and g. said other meansincluding a fluid pressure responsive member carried by said hold-downmeans for movement in one direction to urge said latch structure intosaid locking position, and for movement in the opposite direction toallow lateral movement of the latch structure out of said lockingposition.
 2. The combination of claim 1 wherein said latch structureincludes a circular series of latch dogs received downwardly within saidbody on an annular insert portion of said hold-down means.
 3. Thecombination of claim 2 wherein the lower terminal of said annular insertportion of said hold-down means provides a stop against which the uppersurface of the packer is engageable, said packer including anelastomeric body and metallic inserts carried thereby and having upperplates defining said upper surface.
 4. The combination of claim 1including a sub-sea well head stack mounting said body, and a tubularriser extending upwardly from said hold-down means.
 5. The combinationof claim 4 wherein said riser has connection to said hold-down means forelevating said hold-down means relative to said body and to a positionin which said packer is upwardly openly exposed for removal from thebody.
 6. In well blow-out preventer apparatus, the combinationcomprising a. an annular body adapted to pass well equipment, b. a fluidpressure responsive packer actuator movable in the body, c. an annularpacker received downwardly in the body and supported for generallyradial constriction and expansion in response to actuator movement, d.hold-down means carried to block upward displacement of the packer inresponse to movement of the actuator, e. other means for effectinglocking of the hold-down means to the body and unlocking thereof topermit upward removal of the hold-down means from the body followed bywithdrawal of the packer therefrom, and f. a sub-sea well head stackmounting said body, and a tubular riser extending upwardly from saidhold-down means, said riser having connection to said hold-down meansfor elevating said hold-down means relative to said body and to aposition in which said packer is upwardly openly exposed for removalfrom the body, and said riser connection to the hold-down meanscomprising a ball and socket, the ball defining a vertical passage abovean opening defined by the packer.
 7. The combination of claim 6 whereinsaid hold-down means has telescopic interfit with said body, and saidother means includes latch structure carried by the hold-down means formovement into and out of locking position relative to said body.
 8. Thecombination of claim 7 wherein said other means includes a fluidpressure responsive member carried by said hold-down means for movementin one direction to urge said latch structure into said lockingposition, and for movement in the opposite direction to allow lateralmovement of the latch structure out of said locking position.
 9. Thecombination of claim 6 including packer retrieval means locatedgenerally laterally of said body and riser and having a part bodilymovable laterally and downWardly into said body for lifting the packertherefrom after preliminary elevation of the hold-down means by saidriser.
 10. The combination of claim 9 wherein said part comprises anelectromagnet.
 11. The combination of claim 9 wherein said partcomprises a plug downwardly insertible into a central opening defined bythe packer, and including a lifting element carried by the plug formovement into packer lifting position.
 12. The combination of claim 9including vertically extending guy wires to which the packer retrievalmeans has guided connection for elevation and lowering thereof relativeto the stack.
 13. The combination of claim 9 wherein said packerretrieval means includes a carrier that is vertically movable relativeto the stack, and an arm operatively connected to the carrier andsupporting said part for said bodily movement between lowered positionin which said part projects within said annular body for operativeconnection to the packer, and raised position in which said part and thepacker are laterally offset from the stack for elevation by the carrierto the sea surface.
 14. The combination of claim 13 wherein said arm haspivotal connection to the carrier, and including locating means forlocating the carrier in predetermined relation to the stack in responseto lowering of the carrier laterally of the stack.
 15. The combinationof claim 14 including retention means on the carrier to interfit thepacker in raised position thereof and in response to elevation of thecarrier, for positive retention of the packer on the carrier duringelevation to the surface.
 16. The combination of claim 15 wherein saidretention means comprises a plug sized to upwardly penetrate the centralpassage formed by the packer in said raised position.
 17. Thecombination of claim 15 wherein said carrier comprises a first sectionconnected to said retention means, and a second section to which the armhas said pivotal connection, the second section being movable verticallyrelative to said first section to effect said interfit of the retentionmeans with the packer in response to initial elevation of the carrierrelative to a portion of said locating means attached to the stack. 18.The combination of claim 13 wherein said part is pivotally suspendedfrom said arm.
 19. The combination of claim 13 including an actuator onthe carrier and operable to displace said arm between positionscorresponding to said raised and lowered positions of said part.